From: Sohil Mehta <sohil.mehta@intel.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>, <dave.hansen@intel.com>
Cc: <acme@redhat.com>, <aik@amd.com>, <akpm@linux-foundation.org>,
<alexander.shishkin@linux.intel.com>, <ardb@kernel.org>,
<ast@kernel.org>, <bp@alien8.de>, <brijesh.singh@amd.com>,
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<corbet@lwn.net>, <daniel.sneddon@linux.intel.com>,
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<jgg@ziepe.ca>, <jgross@suse.com>, <jpoimboe@kernel.org>,
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<pawan.kumar.gupta@linux.intel.com>, <peterz@infradead.org>,
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<sandipan.das@amd.com>, <shijie@os.amperecomputing.com>,
<tglx@linutronix.de>, <tj@kernel.org>, <tony.luck@intel.com>,
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<xiongwei.song@windriver.com>, <ytcoode@gmail.com>
Subject: Re: [PATCHv6 07/16] x86/vsyscall: Reorganize the #PF emulation code
Date: Fri, 20 Jun 2025 16:18:28 -0700 [thread overview]
Message-ID: <f6d73a46-7ca0-4898-bb23-9095be403ea9@intel.com> (raw)
In-Reply-To: <262c0fd2-ac66-4ce7-903f-4062f1fe1d6e@citrix.com>
On 6/20/2025 4:08 PM, Andrew Cooper wrote:
>> But, the resulting code is wonky. It needs to do something more like this:
>>
>> if ((error_code & (X86_PF_WRITE | X86_PF_USER)) != X86_PF_USER)
>> return false;
>>
>> if (error_code & X86_PF_INSTR))
>> return __emulate_vsyscall(regs, address);
>
> To do this, LASS needs a proper interlink against NX || SMEP.
>
> If neither NX nor SMEP are active, the CPU does not report X86_PF_INSTR,
> meaning that fetches are reported as plain reads.
>
> This leads to some fun corner cases in SMAP and now LASS too for virt.
Maybe I am missing something, but LASS works pre-paging so it wouldn't
generate a PF, right?
We have a new vsyscall emulation for #GP (patch 9) that wouldn't follow
this path.
next prev parent reply other threads:[~2025-06-20 23:19 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-20 13:53 [PATCHv6 00/16] x86: Enable Linear Address Space Separation support Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits Kirill A. Shutemov
2025-06-20 15:25 ` Dave Hansen
2025-06-20 15:36 ` Xin Li
2025-06-20 17:31 ` Kirill A. Shutemov
2025-06-20 23:46 ` Xin Li
2025-06-21 0:45 ` H. Peter Anvin
2025-06-21 0:50 ` H. Peter Anvin
2025-06-23 17:40 ` Xin Li
2025-06-24 2:04 ` H. Peter Anvin
2025-06-24 4:57 ` Xin Li
2025-06-24 5:11 ` Xin Li
2025-06-20 16:02 ` Randy Dunlap
2025-06-20 16:12 ` Xin Li
2025-06-20 16:16 ` Randy Dunlap
2025-06-20 16:35 ` Borislav Petkov
2025-06-20 17:33 ` Kirill A. Shutemov
2025-06-20 18:29 ` Borislav Petkov
2025-06-23 8:17 ` Kirill A. Shutemov
2025-06-23 10:21 ` Borislav Petkov
2025-06-23 13:42 ` Kirill A. Shutemov
2025-06-26 15:18 ` Borislav Petkov
2025-06-26 16:07 ` Borislav Petkov
2025-06-26 17:21 ` Dave Hansen
2025-06-27 10:25 ` Kirill A. Shutemov
2025-06-27 10:43 ` Borislav Petkov
2025-06-27 13:57 ` Dave Hansen
2025-06-20 18:14 ` Sohil Mehta
2025-06-20 18:24 ` Dave Hansen
2025-06-20 23:10 ` Sohil Mehta
2025-06-23 16:25 ` Luck, Tony
2025-06-23 16:42 ` Dave Hansen
2025-06-23 23:13 ` Luck, Tony
2025-06-23 23:36 ` H. Peter Anvin
2025-06-24 0:10 ` Luck, Tony
2025-06-24 2:03 ` H. Peter Anvin
2025-06-25 18:51 ` H. Peter Anvin
2025-06-20 13:53 ` [PATCHv6 02/16] x86/asm: Introduce inline memcpy and memset Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 03/16] x86/alternatives: Disable LASS when patching kernel alternatives Kirill A. Shutemov
2025-06-20 15:33 ` Dave Hansen
2025-06-20 17:18 ` Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 04/16] x86/efi: Move runtime service initialization to arch/x86 Kirill A. Shutemov
2025-06-20 15:35 ` Dave Hansen
2025-06-20 17:42 ` Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 05/16] x86/cpu: Defer CR pinning setup until after EFI initialization Kirill A. Shutemov
2025-06-20 15:44 ` Dave Hansen
2025-06-20 13:53 ` [PATCHv6 06/16] efi: Disable LASS around set_virtual_address_map() EFI call Kirill A. Shutemov
2025-06-20 15:55 ` Dave Hansen
2025-06-20 17:50 ` Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 07/16] x86/vsyscall: Reorganize the #PF emulation code Kirill A. Shutemov
2025-06-20 18:43 ` Dave Hansen
2025-06-20 23:08 ` Andrew Cooper
2025-06-20 23:18 ` Sohil Mehta [this message]
2025-06-20 23:29 ` Andrew Cooper
2025-06-20 23:21 ` Dave Hansen
2025-06-21 3:35 ` H. Peter Anvin
2025-06-23 12:41 ` Kirill A. Shutemov
2025-06-23 12:46 ` Andrew Cooper
2025-06-23 15:32 ` Dave Hansen
2025-06-23 15:45 ` Andrew Cooper
2025-06-24 11:37 ` Kirill A. Shutemov
2025-06-24 14:11 ` Dave Hansen
2025-06-24 14:59 ` [PATCH] x86/vsyscall: Do not require X86_PF_INSTR to emulate vsyscall Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 08/16] x86/traps: Consolidate user fixups in exc_general_protection() Kirill A. Shutemov
2025-06-20 14:47 ` Dave Hansen
2025-06-20 13:53 ` [PATCHv6 09/16] x86/vsyscall: Add vsyscall emulation for #GP Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 10/16] x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 11/16] x86/cpu: Set LASS CR4 bit as pinning sensitive Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 12/16] x86/traps: Communicate a LASS violation in #GP message Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 13/16] x86/traps: Handle LASS thrown #SS Kirill A. Shutemov
2025-06-20 15:20 ` Xin Li
2025-06-20 17:53 ` Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 14/16] x86/cpu: Make LAM depend on LASS Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 15/16] x86/cpu: Enable LASS during CPU initialization Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 16/16] x86: Re-enable Linear Address Masking Kirill A. Shutemov
2025-06-20 15:38 ` [PATCHv6 00/16] x86: Enable Linear Address Space Separation support Dave Hansen
2025-06-20 22:04 ` Andrew Cooper
2025-06-20 22:29 ` H. Peter Anvin
2025-06-20 22:43 ` H. Peter Anvin
2025-06-20 22:46 ` Dave Hansen
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